Anti-back-up device for work carriers on power-and-free conveyor systems

ABSTRACT

A work carrier for a power-and-free conveyor system has antiback-up means comprising a pair of serrated cams mounted on the carrier frame and weight-biased into one-way frictional engagement with the undersurfaces of the track channels.

United States Patent [1 1 Desilets [451 Sept. 18, 1973 ANTI-BACK-UPDEVICE FOR WORK CARRIERS ON POWER-AND-FREE CONVEYOR SYSTEMS [75]Inventor: Dennis W. Desllets, Sterling Heights,

Mich.

[73] Assignee: Standard Alliance Industries, Inc.,

Chicago, 11].

[22] Filed: Sept. 14, 1971 [21] Appl. No.: 180,401

UNITED STATES PATENTS 3200;768 8/1965 Harrison 104/172 S 2,326,3778/1943 McBride 188/67 3,415,201 12/1968 Czarnecki.... 104/172 S2,623,614 12/1952 Herr 188/44 648,258 4/1900 Hill l88/43 PrimaryExaminer-Robert G. Sheridan Assistant Examiner-Lawrence J. OreskyAttorney-Harness, Dickey & Pierce [5 7] ABSTRACT A work carrier for apower-and-free conveyor system has anti-back-up means comprising a pairof serrated cams mounted on the carrier frame and weight-biased intoone-way frictional engagement with the undersurfaces of the trackchannels.

2 Claims, 2 Drawing Figures PATENTEDSEPIBW 3.759.189

SHEET 1 BF 2 I INVENIOR. I077: 14/ Jaszfifs PATENTED SEP l-8l973 sum 20F 2 INVENTOR.

j 77712.? V/Jesf/az ANTI-BACK-UP DEVICEFOR WORK CARRIERS ONPOWER-AND-FREE CONVEYOR SYSTEMS BACKGROUND OF THE INVENTION Theinvention relates to power-and-free conveyor systems of the type shownin U. S. Pat. No. 3,415,201 issued Dec. I0, 1968 to A. Czarnecki. Theinvention is particularly applicable to work carriers having front andrear trolleys constructed so as to permit closepacking or accumulation,and which pass through transfer points.

Among the problems existing with respect to such conveyor systems is thedanger of a carrier inadvertently backing up. This could be due to thependulum effect of the load when a carrier is being nested. In othercases, the carrier could be inadvertently released from its pusher on aslope or at a transfer point. Backing up could also occur in case ofdriving chain breakage.

BRIEF SUMMARY OF THE INVENTION 3 According to the invention, a pair ofcams are rockably mounted on the trolley frame of a work carrier, inthis case on the rear trolley of a work carrier having front and reartrolleys connected by a load bar. The cams have serrated edgesengageable with the lower flanges of the track channels, and are locatedbetween the load carrying wheels of the trolley, thus acting as atrolley hold-down and preventing the cam plate from tipping up inaccumulation. The provision oftwo antiback-up cams on each carriercompensates for the presence of auxiliary devices required on certainsystems which extend below the channel flanges and might disengage oneof the cams.

The result is an anti-,back-up device which positively prevents a workcarrier from backing up in accumulation and at transfer pointsregardless of the speed of the conveyor of the inertia induced in thecarriers. The pendulum action of the workpiece is quickly dissipated dueto the stabilizing effect the anti-back-up cams have on the load bar.The anti-back-up cams also allow accumulation of carriers on slightvertical inclines without the use of any auxiliary equipment. Thelocation of the cams under the channels increases reliability becausethe only tolerance which need be taken into account is that of the lowerflange thickness of the channels. Additionally, the space availableunder the channels allows provision of an effective anti-back-up device.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENT The invention is especially adapted for use with apower-and-free conveyor system of the type shown in the aforementionedUS. Pat. No. 3,415,201. In such a system, a plurality of trolley-typework carriers generally indicated at 11 from which workpieces (notshown) are suspended are movable along an overhead track generallyindicated at 12. A power driven chain (also not shown) or the like islocated adjacent the work carriers and is provided with spaced pushermembers selectably engageable with and disengageable from the workcarriers in a predetermined manner to effect the desired workpiecedelivery along paths defined by the track, in the direction of the arrow13 of FIG. 1. To provide nesting or close-packing of the workpieces,each work carrier comprises interconnected front and rear trolleys, therear trolley of one carrier 11 being indicated generally at 14. Thistrolley is connected to the front trolley (not shown) by a load barindicated partially at 15 below track 12.

Track 12 comprises a pair of spaced channels 16 and 17 in facingrelation, each channel having an upper flange l8 and a lower flange 19.Rear trolley 14 has a frame generally indicated at 21 extending betweentracks 16 and 17. The frame has two pairs of wheels 22 and 23 in spacedrelation, these wheels being disposed within channels 16 and 17 andresting on lower flanges 19. A pair of guiding rollers 24 and 25 arecarried by frame 21 between flanges 19 for lateral stability of thetrolley. A cam plate 26 surrnounts frame 21 and is disposed above track12. As described further in the aforementioned patent, this cam plate isbifurcated and otherwise so shaped as to accomplish the close-packing ornesting function of adjacent work carriers.

Frame 21 has a depending portion 27 below the portion 28 thereofconnected to load bar 15. A shaft 29 extends through frame portion 27beneath track 12. A pair of bushings 30 and 31 are mounted on this shaftand rockably support a pair of anti-back-up cams indicated generally at32 and 33 respectively.

These cams are of identical construction, each having an upwardlyextending portion 34 with a slightly convex serrated upper edge 35, theteeth of which may be slightly crowned. The curvature of edge 35 is suchthat its leading end 36 is closer to the axis of shaft 29 than is itstrailing end 37. The thickness of portion 34 is relatively small, ascompared with a weighted portion 38'which extends below shaft 37. Theweighted portion thus tends to hold serrated edge 35 against theundersurface 39 of flange 19. The cams are held in place by washers 41,nuts 42 and cotter pins 43.

A stop 44 projects from each side of frame 21 and is engageable by ashoulder 45 when cam 32 or 33 swings clockwise from its FIG. 1 position.This will prevent the cam from flipping over. Should the dimensionbetween shaft 28'and surface 39 increase due to wear or some otherreason, stop 44 will engage the other end of surface 45, preventing thecam from flipping counterclockwise. It should be noted that if eithercam were to flip around in either direction and cause edge 35 torecontact surface 39, conveyor flow in the direction of arrow 13 wouldbe prevented.

In order for the device to operate properly for a load of greatmagnitude, the rigidity of shaft 29 must be such Otherwise, the dangerexists that edges 35 will not properly grip surfaces 39.

In operation, cams 32 and 33 will be inactive during I the normalpowered movement of work carrier 11 in the direction of arrow 7 13.During such movement, edges 35 will be lightly dragged alongundersurfaces 39 of track channel flanges 19. However, should there beany tendency for the work carrier to move in a direction opposite thatof arrow 13, the teeth of serrated edges 35 will immediately bite intoundersurfaces 39 and prevent such retrogression.

It should be observed that the relatively small tolerance involved inthe thickness of flanges 19 will make it extremely easy to achieveproper locking action of the back-up cams, and that the generous spaceavailable beneath track 12 will permit the cams to be of an efficientshape. The location of earns 32 and 33 between the load carrying wheels22 and 23 of trolley 14 permit the cams to act as a hold-down for thetrolley and to prevent cam plate 26 from tipping upwardly during theprocess of nesting or accumulation.

I claim:

1. In an anti-back-up construction for use with work carriers of thetype having a trolley carried by a track,

at least one cam rockably mounted on said work carrier beneath saidtrack, said cam having an upper portion with a frictional edgeengageable with the undersurface of the track, means constantly urgingthe frictional edge into engagement with the track, the frictional edgebeing so shaped as to freely permit work carrier movement in a forwarddirection but preventing backup movement by frictional engagement withthe track, said cam having a shoulder thereon, and a stop extending fromsaid work carrier and engageable by said shoulder to prevent said camfrom flipping over in either direction.

2. The combination according to claim 1, wherein the work carrier has apair of cams mounted on opposite sides thereof.

1. In an anti-back-up construction for use with work carriers of thetype having a trolley carried by a track, at least one cam rockablymounted on said work carrier beneath said track, said cam having anupper portion with a frictional edge engageable with the undersurface ofthe track, means constantly urging the frictional edge into engagementwith the track, the frictional edge being so shaped as to freely permitwork carrier movement in a forward direction but preventing back-upmovement by frictional engagement with the track, said cam having ashoulder thereon, and a stop extending from said work carrier andengageable by said shoulder to prevent said cam from flipping over ineither direction.
 2. The combination according to claim 1, wherein thework carrier has a pair of cams mounted on opposite sides thereof.